Milling head and methods for tube end preparation

ABSTRACT

A milling head for use in conjunction with a rotary milling tool that is utilized to perform an operation on a tube, preferably of a tube bank or tube wall of a boiler system. The milling head is utilized to remove material or film from the outer diameter of a tube, or place a bevel on a tube end, or both. In one embodiment, the milling head includes at least one outer diameter milling element and at least one bevel milling element that are adjustable in relation to each other as well as the milling head body. Methods for milling a tube are also described.

CROSS-REFERENCE

This application is a continuation application of pending U.S. patentapplication Ser. No. 11/256,125, filed Oct. 21, 2005 for MILLING HEADAND METHODS FOR TUBE END PREPARATION.

FIELD OF THE INVENTION

The present invention relates to a milling head for use in conjunctionwith a rotary milling tool that is utilized to perform an operation on atube, preferably of a tube bank or tube wall of a boiler system. Themilling head is utilized to remove material or film from the outerdiameter of a tube, or place a bevel on a tube end, or both. In apreferred embodiment, the milling head includes at least one outerdiameter milling element and at least one bevel milling element that areadjustable in relation to each other as well as the milling head body.Methods for milling a tube are also described.

BACKGROUND OF THE INVENTION

Power generating or other plants circulate fluids, such as water orsteam, through tubes or banks of tubes. The fluid is often heated andused, for example, to drive turbines which generate electricity.

The tubes are generally arranged in large panels or banks of paralleltubes which are connected together with a metal membrane or webcontinuously interposed between each pair of adjacent tubes in the bankto form a tube wall. The tubes generally have an outer diameter whichcan range from about 1 inch up to about 3 inches, with a wall thicknesswhich can be up to about 0.5 inch. The web or membrane connectingadjacent tubes to each other generally has a thickness about equal tothe wall thickness of the tubes, with the width of the webbing generallyranging from about 0.25 inch to about 0.75 inch. The webs or membranesare generally welded to the outer walls of adjacent tubes to form thetube banks. In some cases a weld overlay comprising a metal or alloy ispresent on portions of the tube bank in an effort to prevent corrosionor deterioration. The weld overlay is present on both sides of a tubebank in some embodiments. On account of deterioration due to corrosionand the like, the tubes occasionally require replacement. Ordinarily,repair of damaged or worn tubing involves cutting and removal ofrelatively large sections of the tube banks, and replacement with a newpanel of tubes. The bank sections are generally replaced in largerectangular sections typically having sizes ranging from a few feet to10, 20, 100 or even 200 feet in length.

The sections of tube banks which are to be replaced are generally cutout using a power saw or a cutting torch. A method and apparatus forcutting out a section of boiler tube wall is illustrated and describedin U.S. Pat. No. 5,033,347, herein fully incorporated by reference.

After the damaged or worn section of tube wall which is to be replacedhas been cut out and removed, it is necessary to properly prepare thetube ends exposed by removal of the old section before positioning thenew tube bank section in the tube wall opening. Proper preparation ofthe exposed tube ends of the existing boiler tube wall requireschamfering or beveling of the exposed tube ends to facilitate a goodweld between the new tube wall section and the existing boiler tubewall. More specifically, the adjoining tube ends of the existing tubewall and those of the new or replacement section of tube wall should beprovided with a frustoconical bevel so that when the adjoining tube endsare placed in alignment, a circumferential groove is formed to receivemolten metal from the welding rod. The replacement section of tube wallis usually fabricated and prepared for welding off-site before thedamaged or worn section of existing tube wall is removed. The exposedtube ends of the existing tube wall, however, must be prepared forwelding on-site, often in a confined space. It is highly desirable thatall work performed on the existing tube wall be conducted as quickly andefficiently as possible so as to minimize the period during which thesteam generator is taken out of service for repair. Accordingly,preparation of the exposed tube ends of the existing tube wall forwelding is generally accomplished using portable hand-held milling toolssuch as those disclosed in U.S. Pat. Nos. 4,449,871 and 4,889,454,herein fully incorporated by reference.

To facilitate rapid and efficient chamfering or beveling of the exposedtube ends of the existing tube wall using conventional milling tools,and to provide ample space between vertically adjacent tubes for weldingaround the entire circumference of the tube ends, it is highly desirableand generally necessary to remove a portion of the membrane between eachpair of exposed tube ends of the existing tube wall. Typically, it isdesirable to remove the membrane between adjacent tube ends, which areexposed by removal of the damaged wall section, from the horizontallycut edge of the existing boiler tube wall to a depth which is at leastequal to the depth of the frustoconical bevel which is to be milled atthe tube end. Typically, membrane material is removed from thehorizontally cut edge between two adjacent tubes to a depth of about ⅜inch, about ¾ inch, or about 1 inch or more from the cut edge.

Membrane removal utilizing rotary milling tools on an existing tube of atube wall has been limited to a cutting sweep equal to the outer radiusof a tube. An example of a membrane milling head is set forth in U.S.Pat. No. 5,542,177 to Mark Hillestad. After the membrane material, weldoverlay material removal, or outer diameter tube film removal, afrustoconical bevel is milled on the tube around the entirecircumference thereof.

U.S. Pat. No. 6,955,507 to Hall relates a milling head adapted to removetube material from the outer diameter of a tube, in addition to anymembrane or weld overlay present on the surface of a tube. In a furtherembodiment, the milling head is adapted to place a bevel on a tube end.

Afterwards, a second tube with a corresponding bevel is matched with thefirst beveled tube and the tubes are welded together by molten metal orsolder placed around the joined tubes, especially at the circumferentialgroove formed by the adjoined beveled tube ends.

It would be beneficial to form a strong durable weld between joinedtubes having beveled or chamfered ends.

SUMMARY OF THE INVENTION

The present invention relates to a milling head adapted to be connectedto a rotary milling tool. The milling head preferably includes an outerdiameter milling element that can be adjusted in a track of a millingelement support of the milling head and fixed at a desired location onthe milling head. The outer diameter milling element is adapted toremove material from the outer portion, such as the outer diameter orcircumference, of a tube end portion. The outer diameter milling elementcan also optionally remove membrane or overlay material if present onthe outer surface of the tube. In one embodiment, the outer diametermilling element has at least one cutting edge adapted to mill from about1% to about 50% of the tube radial thickness measured from the innerradius to the outer radius of the tube perpendicular to the centralaxis. The outer diameter milling element cutting edge(s) can beconfigured to impart a desired finish to a portion of the tube end.

The milling head preferably also includes a bevel milling elementadapted to impart a beveled edge or finish on an edge of the tube. Thebevel milling element can be adjusted in a channel of the millingelement support of the milling head and fixed at a desired location andangle with respect thereto.

In a further embodiment of the present invention, a gauge is provided toassist a user in arranging and setting the milling elements of themilling head in a particular orientation. Methods for utilizing thegauge are described.

Accordingly, it is an object of the present invention to provide amilling head having milling elements adapted to remove tube material orfilm from an outer portion of the tube, or bevel a tube end, orcombinations thereof.

A further object of the present invention is to provide methods forpreparing or cleaning an end portion of a tube for a subsequent weldoperation utilizing a milling head of the present invention. The tubematerial removal step provides a beneficial bonding surface withoutsubstantially weakening the tube.

Yet another object of the present invention is to provide a milling headhaving milling elements that can be easily adjusted in order to mill adesired finish on an end portion of a tube. A milling head is providedwherein an outer diameter milling element is adjustable in relation tothe milling head. In an additional embodiment, a bevel milling elementis provided that is adjustable in relation to the milling head. Millingheads of the present invention are capable of performing operationssimultaneously thereby enabling a user to efficiently complete tubepreparation.

A further object of the present invention is to provide methods forarranging or setting the milling elements of the milling head,particularly utilizing a gauge.

Accordingly, one aspect of the present invention relates to a millinghead for a rotary milling tool, comprising a body adapted to beconnected to a rotary milling tool, wherein the body has an annularrecess, and one or more milling element supports connected to the body,wherein at least one milling element support includes a channel, whereina bevel milling element having a cutting edge is adjustable in thechannel, wherein the bevel milling element is connected to the channel,wherein at least one milling element support includes a guide, whereinan outer diameter milling element having a cutting edge is adjustable inrelation to the guide, wherein the outer diameter milling element isconnected to the guide, wherein the bevel milling element has an annularcutting sweep that is at least concentric with an inner end of a cuttingsweep of the outer diameter milling element and radially inward adistance from the outer diameter milling element cutting sweep.

Another aspect of the invention is a milling head for a rotary millingtool, comprising a body having an annular recess, the body adapted to beconnected to a rotary milling tool; one or more milling element supportsconnected to the body, wherein the milling element support includes aguide; and an outer diameter milling element having a cutting edgeadapted to remove material from an outer diameter of a tube, wherein theouter diameter milling element is adjustable in relation to the guideand is secured between the guide and a fixing element, wherein thefixing element is connected to the milling element support by a securingelement.

Yet another aspect of the invention is a milling head for a rotarymilling tool, comprising a body adapted to be connected to a rotarymilling tool; and at least one milling element support connected to thebody, wherein the milling element support is spaced a distance from acentral rotational axis of the milling head, wherein a recess extends adistance between the milling element support and the central rotationalaxis, wherein the milling element support includes a channel, andwherein the channel has a back wall that longitudinally extends inrelation to the central rotational axis of the milling head at an angleof 0° to about 45°; and wherein a bevel milling element having a cuttingedge adapted to mill a bevel on a tube is secured in the channel.

A further aspect of the invention is a method for milling a tube,comprising the steps of providing a tube having an end portion;providing a rotary tool having a milling head comprising a body adaptedto be connected to a rotary milling tool, wherein the body has anannular recess, and one or more milling element supports connected tothe body, wherein at least one milling element support includes achannel, wherein a bevel milling element having a cutting edge isadjustable in the channel, wherein the bevel milling element isconnected to the channel, wherein at least one milling element supportincludes a guide, wherein an outer diameter milling element having acutting edge is adjustable in relation to the guide, wherein the outerdiameter milling element is connected to the guide, wherein the bevelmilling element has an annular cutting sweep that is at least concentricwith an inner end of a cutting sweep of the outer diameter millingelement and radially inward a radial distance from the outer diametermilling element cutting sweep; adjusting at least one of the outerdiameter milling elements or bevel milling elements in relation to themilling head body and securing the at least one element to the millinghead; and milling the end portion of the tube by removing material froman outer diameter of the tube and placing a bevel on the end of thetube.

BRIEF DESCRIPTION OF THE DRAWINGS

The preferred embodiment of the invention, illustrative of the best modewhich applicants have contemplated, is set forth in the followingdescription and is shown in the drawings and is particularly anddistinctly pointed out and set forth in the appended claims.

FIG. 1 is a top view of a portion of a tube wall illustrating tube ends,in various states of finish, which have been exposed by removal of asection of the tube wall.

FIG. 2 is a front elevational view of the tube wall of FIG. 1.

FIG. 3 is a side elevational view of one embodiment of a milling head ofthe present invention located above a tube milled therewith.

FIG. 4 is a bottom view of one embodiment of a milling head of thepresent invention.

FIG. 5 is a top view of one embodiment of a milling head of the presentinvention.

FIG. 6 is a partial side view of the outer diameter milling element atdifferent positions with respect to a milling element support.

FIG. 7 is a partial side view of the bevel milling element at differentpositions with respect to a milling element support.

FIG. 8 is a side view of a gauge that is utilized to adjust the millingelements in one embodiment.

FIG. 9 is a bottom view of the gauge shown in FIG. 8.

FIG. 10A is a front elevational view of one embodiment of a millingelement having a slotted bore.

FIG. 10B is a front elevational view of one embodiment of a millingelement having a slotted bore.

FIG. 11 is a partial side view of an outer diameter milling elementhaving a slotted bore fixable at a plurality of positions with respectto a milling element support.

FIG. 12 is a partial side view of the bevel milling element having aslotted bore fixable at a plurality of positions with respect to amilling element support.

DETAILED DESCRIPTION OF THE INVENTION

This description of preferred embodiments is to be read in connectionwith the accompanying drawings, which are part of the entire writtendescription of this invention. In the description, correspondingreference numbers are used throughout to identify the same orfunctionally similar elements. Relative terms such as “horizontal,”“vertical,” “up,” “down,” “top” and “bottom” as well as derivativesthereof (e.g., “horizontally,” “downwardly,” “upwardly,” etc.) should beconstrued to refer to the orientation as then described or as shown inthe drawing figure under discussion. These relative terms are forconvenience of description and are not intended to require a particularorientation unless specifically stated as such. Terms including“inwardly” versus “outwardly,” “longitudinal” versus “lateral” and thelike are to be interpreted relative to one another or relative to anaxis of elongation, or an axis or center of rotation, as appropriate.Terms concerning attachments, coupling and the like, such as “connected”and “interconnected,” refer to a relationship wherein structures aresecured or attached to one another either directly or indirectly throughintervening structures, as well as both movable or rigid attachments orrelationships, unless expressly described otherwise. The term“operatively connected” is such an attachment, coupling or connectionthat allows the pertinent structures to operate as intended by virtue ofthat relationship.

There is shown in FIGS. 1 and 2 a portion of a boiler tube wall 10 fromwhich a section has been cut out to expose tube ends 12. The boiler tubewall 10 is comprised of a row of parallel, typically vertically orientedtubes 14, each of which is connected to an adjacent tube by a web ormembrane 16. The tubes 14 and membranes 16 are generally formedseparately of metal or alloy such as steel and then welded together.Repair of boiler tube walls generally involves cutting out a section ofthe tube wall which is worn or damaged, chamfering or beveling the tubeends which have been exposed by removal of the worn or damaged sectionof tube wall, and welding a new or replacement section of tube wall inplace of the damaged section which has been removed. The damaged sectionof tube wall is usually removed by making two horizontally spaced cutstransverse to the longitudinal direction of the tubes 14 and twovertically spaced cuts, which together with the horizontal cuts define arectangular section which is to be replaced. Before a new or replacementsection of the wall can be installed, it is necessary to prepare thetube ends for welding by first removing membrane material from betweenthe tube ends, beveling the tube ends, and also performing a tube filmremoval or diameter cleanup step extending a predetermined distancebelow a beveled portion, or portion to be beveled. It is to beunderstood that the milling heads and methods of the invention apply toindividual tubes, pipes, or the like, as well as two or more tubesconnected such as in a tube bank.

In some embodiments, a tube will include a weld overlay 17, either onone or both sides of a tube wall as shown in FIG. 1. The weld overlay 17is typically a metal coating, such as a pure metal, but more typicallyan alloy material such as Inconel® (Inco Alloy/Special Metals) or otheralloy which are well known to the art and to the literature, applied tothe tube wall to protect against tube corrosion and/or wear. The weldoverlay 17 is of varying thickness as it is generally not preciselyapplied. Accordingly, the weld overlay 17 must be removed in some casesto prepare the tube ends 12 for welding, even though difficult toremove.

A milling head of the present invention is attached to a rotary millingdevice or power-tool as known in the art. Rotary milling devices arewell known in the art and are commercially available from sources suchas H&S Tool of Wadsworth, Ohio. Examples of rotary milling toolsinclude, but are not limited to, Model MB, Model MS, Model B, Model MT,and Model MFT. Rotary milling devices are generally electrically orpneumatically powered.

In one embodiment, a membrane cutting rotary milling head such asdescribed in U.S. Pat. No. 5,542,177, herein fully incorporated byreference, is utilized to remove membrane material from between tubes.The inner radius of the annular cutting sweep of the membrane millinghead is preferably greater than the outer radius of the tube wall to bemilled. The membrane milling head is utilized to remove membrane 16 aswell as any weld overlay 17 if present on the outer surface of the tube.

In one embodiment of the present invention, as shown in FIGS. 3, 4 and5, a milling head 30 is configured to mill a tube, pipe or the like andimpart a desired finish thereto. Milling head 30 is adapted to place orimpart a beveled edge or area 13 onto an end 12 of the tube 10, orremove tube material from the outer diameter of the tube 10, or acombination thereof, depending on the milling elements connectedthereto, such as an outer diameter milling element 50 or a bevel millingelement 60. The outer diameter tube material or film removal step cuts,grinds, shaves, abrades, or otherwise removes a film or thin annulusfrom the outer surface 11 of the tube 10, preferably substantiallycompletely or completely around the circumference thereof. That is, aportion of the tube outer diameter is removed, preferably in addition toany weld overlay 17 material and/or membrane 16 material optionallypresent on or partially surrounding the tube 10 in the area where thediameter clean-up step is performed.

As shown in FIG. 5, the milling head 30 includes a tool mounting portion32 at the upper end of milling head 30. Tool mounting portion 32includes bore 34 which can be operatively connected to rotary gearing ofa rotary milling tool. Bore 34 further allows for passage of a rod, acollet or other rotary tool securing mechanism, as known in the art,that can be utilized to operatively secure the rotary milling tool andthus rotary milling head 30 in relation to a tube 10 to be milled asknown in the art. In one embodiment, bore 34 includes a key slot 36which is adapted to matingly engage a key on the rotary milling tool tolock the milling head 30 to the rotary tool rotary gearing. Variousother means for mounting a milling head are known in the art and canalternatively be utilized. Set screw 38 is optionally utilized tomaintain engagement of the rotary milling tool with milling head 30.

The milling head 30 of the present invention has a configuration ordesign which allows the milling elements 50, 60 thereof to mill aportion of a tube 10, as well as any weld overlay 17 and/or membrane 16that is present on one or more sides of the tube. The outer diametermilling element 50 has a cutting edge 51 which is self-cleaning andprovides for continuous cutting of surfaces, especially continuous orsemi-continuous surfaces such as, but not limited to, tubecircumference, weld overlay and membrane. Self-cleaning cutting edgesare known to the art and to the literature and have the ability tosubstantially prevent the head from seizing, catching, and/or stoppingduring operation but rather shed pieces, chips, or shavings, or the likeaway from the milling element cutting surfaces preferably allowingcontinuous, uninterrupted cutting and rotation.

Milling head 30 includes a base 40 that extends desirably in a radialdirection, and preferably in a perpendicular direction when compared tocentral axis 31 about which the milling head is adapted to rotate. Base40 is a platform to which the milling elements 50 and 60 are operativelyconnected, when present. One or more milling element supports 42 areconnected to base 40 as shown in at least FIG. 3. Generally from 1 toabout 10, desirably 2 to about 4, and preferably 3 supports 42 areutilized on milling head 30. An outer diameter milling element 50 orbevel milling element 60, or both, can be attached to each millingelement support 42 if desired. The milling element support 42 extends apredetermined distance from base 40, preferably in a direction generallyparallel to the central axis 31. The overall length of milling elementsupport 42 can vary and generally depends upon the depth to which theouter diameter of the tube is to be milled, measured from the tube end.Milling element support 42 has a length generally from about 0.5 inches(1.27 cm) to about 6 inches (15.24 cm), desirably from about 1 inch(2.54 cm) to about 4 inches (10.20 cm), and preferably from about 1.5inches (3.81 cm) to about 2.5 inches (6.35 cm). The outer portion ofmilling element support 42 is generally annular and preferably coextendscircumferentially with base 40 as illustrated in FIG. 4. The millingelement supports 42 are preferably arranged along or around the outercircumference of base 40, to allow a tube to fit within and be milledwhile in tube recess or bore 46.

Milling head 30 of the present invention includes outer diameter millingelement 50 in one embodiment that is designed to remove tube material orfilm from the outer surface or diameter of the tube and optionally weldoverlay 17 material, or membrane 16 material, or a combination thereof,to a predetermined depth measured from a tube end 12. Tube material isremoved from the outer diameter to a depth measured from the tube end 12of generally from about 0.25 inches (0.63 cm) to about 4 inches (10.20cm) and desirably to a depth of from about 0.375 inch (0.95 cm) to about1.5 inches (3.81 cm). The outer diameter milling element 50 includes oneor more cutting edges 51, 57, see FIG. 6, that remove an outer radialportion, of the tube in a range generally in an amount from about 1% orabout 2% up to about 20%, or about 50%, desirably up to about 15%, andpreferably up to about 5% or 10% of the total tube radial thickness(annulus) measured from the inner radius to the outer radius of the tubeperpendicular to the central axis 31. The tube outer diameter materialremoval step exposes the clean, bare-metal surface on the outer portionof the tube in the milled area. Rust, scale, debris or the like isremoved during the outer diameter tube milling step. The milled tubesurface provides a strong bonding area for a subsequent weldingoperation.

The outer diameter milling element 50 is connected to milling elementsupport 42, such as shown in FIGS. 3, 4 and 6. Outer diameter millingelement 50 can be adjusted to any of a plurality of positions on millingelement support 42 and then fixed thereto. In a preferred embodiment,milling element support 42 includes an outer diameter milling elementguide 52 having a back 53 which extends generally in a plane radial tocentral axis 31, as shown in FIG. 4, or another angle in relationthereto. Milling element support 42 includes a track 54 that extendsfrom milling element support 42, preferably substantially perpendicularto the plane of back 53 as shown in FIG. 6, and can function as a seator bench for outer diameter milling element 50 and also aids inco-aligning multiple milling elements 50, as each milling elementsupport 42 is preferably provided with a track 54. The outer diametermilling element 50 has an edge 56 that is movable along track 54 in oneembodiment in order to aid in setting outer diameter milling element 50in a desired alignment.

Outer diameter milling element 50 is adjusted to a desired position onguide 52 and secured with fixing element 58. As illustrated in FIG. 4,the outer diameter milling element is secured between back 53 of support42 and fixing element 58. Fixing element 58 is secured to millingelement support 42 through one or more securing elements 70, preferablya threaded screw or bolt connectable in a threaded bore of millingelement support 42. Thus, fixing element 58 secures the outer diametermilling element 50 to the milling element support 42 at a desiredlocation in relation thereto. It is preferred that a cutting edge 51 ofouter diameter milling element 50 extends radially inward from millingelement support 42 as shown in FIG. 6 to provide the desired outerdiameter material removal. In one embodiment, the fixing element 58 hasa foot 59, see FIG. 6 that extends into recess 44 of milling elementsupport 42 that serves to aid in locking the fixing element 58 and outerdiameter milling element 50 to milling element support 42. Guide track54 extends longitudinally at an angle perpendicular to central axis 31,generally from about 0° to about 35°, desirably from about 0° to about20°, and preferably from about 0° to about 15°. An angle of about 15° isshown in FIG. 6. The amount of material removed from the outer diameterof a tube by outer diameter milling element 50 can be controlled andprecisely adjusted to obtain a desired result.

Outer diameter milling element 50 can have any shape or configuration,including, but not limited to, a triangle, a square, a rectangle, acircle, any geometric or non-geometric shape, or an element with one ormore curved or angled surfaces or both, or combinations thereof, inorder to impart a desired finish on the outer diameter of a tube. Forexample, a triangular outer diameter milling element 50 is illustratedin FIGS. 3, 4 and 6, and square and circular outer diameter millingelements 50 are illustrated in FIGS. 10A and 10B, respectively. In apreferred embodiment, it is desirable to provide an outer diametermilling element 50 having a cutting edge 51 that is adapted to impart arelatively non-abrupt curved, rounded, or arced shoulder 15 as shown inFIGS. 2 and 3, as opposed to a shoulder having about a 90° angle. In oneembodiment, a triangular outer diameter milling element 50 is utilizedto form the desired shoulder configuration as shown in FIG. 3. Outerdiameter milling element 50 includes a cutting edge 51 having alongitudinal axis that is situated at an angle with respect to centralaxis 31, generally from about 0° to about 30°, desirably from about 2°to about 20°, and preferably from about 5° to about 15°. As illustratedin FIG. 3, the lower end of cutting edges 51 and 57 are utilized tocreate shoulder 15 on tube 10.

In a further embodiment, outer diameter milling element 50 is providedwith an elongated or slotted bore 72, see FIGS. 10A, 10B and 11 forexample. Outer diameter milling elements 50 having a slotted bore arepreferably utilized with the elongated axis of the slot arrangedparallel to milling element support track 54. As illustrated in FIG. 11,a securing element 70 connects outer diameter milling element 50 to anaperture in milling element support 42. Accordingly, the slotted bore 72allows outer diameter milling element 50 to be adjusted in relation tomilling element support 42 to provide a desired finish on a tube. Theheight of the slotted bore 72, i.e. perpendicular to the elongated axis,is preferably slightly greater than the diameter of the securing element70 designed to secure the milling element 50 to the milling head 30.Slotted bore 72 is preferably countersunk to allow at least a portion ofa head or end portion of the securing element, and preferably the entireend portion to be flush or recess mounted on the milling element 50 in afastened position. The length of the slot can vary depending on the sizeof the outer diameter milling element and ranges generally from about0.10 inch (0.25 cm) to about 0.30 inch (0.76 cm), desirably from about0.15 inch (0.38 cm) to about 0.25 inch (0.64 cm), and preferably fromabout 0.18 inch (0.45 cm) to about 0.20 inch (0.51 cm).

In one embodiment, bevel milling element 60 is adjustably and removablyconnected to milling element support 42 in order to allow milling head30 to mill a bevel onto an end of a tube, such as shown in FIGS. 1, 2and 3. Bevel milling element 60 is capable of being secured to millingelement support 42 at a plurality of positions in relation thereto aswell as to base 40. In one embodiment, bevel milling element 60 issecured in a channel 62 of milling element support 42. Channel 62 isgenerally defined by side 63, back 64, and locking element 68. Back 64,formed generally as a wall, extends along milling element support 42 ina direction parallel to central axis 31 or at an angle with respectthereto, generally at an angle from about 0° to about 45°, desirablyfrom 0° to about 20° and preferably 0° to 10° with respect to thecentral axis 31. In a preferred embodiment, one edge or portion of bevelmilling element 60 is seated against back 64 and moved therealong to adesired position, and then secured to milling element support 42.

A portion of bevel milling element 60 is also adjustable in and alongchannel 62 in a plurality of directions in relation to central axis 31.Bevel milling element 60 is movable in a direction parallel and/orperpendicular to central axis 31 or back 64 or at an angle with respectthereto, and generally from about 0° to about 45°, desirably from 0° toabout 20° and preferably 0° to 10° with respect to the central axis 31,so long as a portion of the bevel milling element 60 remains in channel62 and can be secured to milling element support 42. Accordingly, themilling head 30 of the present invention is versatile and the bevelmilling element 60 can be easily set at a desired position and securedby a user to achieve a desired bevel on a tube end.

Channel 62 of milling element support 42 includes at least one side 63,and a back 64 which generally faces central axis 31. In a preferredembodiment, the plane of side 63 is substantially radial to central axis31 of milling head 30 as shown in FIG. 4. It is preferred that one end69 of bevel milling element 60 abut back 64, but as disclosedhereinabove, the bevel milling element 60 is adapted to be placed adesired distance away from back 64 if required for a particularapplication.

Cutting edge 61 of bevel milling element 60 is arranged at apredetermined angle in relation to milling head 30 central axis 31 inorder to provide a tube end with a desired frustoconical bevel angle.The cutting edge 61 is fixed at an angle generally from about 20° toabout 60°, desirably about 30° to about 45°, and preferably about 37.5°in relation to central axis 31 of milling head 30. The bevel millingelement 60, cutting edge 61 is generally positioned at a radial distanceat least equal to and inward from the innermost cutting surface of outerdiameter milling element 50, as illustrated in FIG. 4, and furtherextending inwardly a predetermined distance toward central axis 31. Theactual annular cutting sweep of the at least one bevel milling element60 is generally at concentric with, i.e. at least equal in radius to,and further extending a distance radially inward of the cutting sweep ofouter diameter milling element 50 cutting edge 51 in order to provide atube end 12 that transitions directly from a beveled area 13 to an area18 where the outer diameter tube film has been removed, as shown in FIG.3.

In one embodiment, bevel milling element 60 is secured directly tomilling element support 42 by a securing element 70, such as illustratedin FIG. 12, preferably through side 63. The securing element 70 isplaced through an aperture in bevel milling element 60 and secured in abore, preferably threaded, in milling element support 42. The aperture74 can be sized to only accommodate securing element 70 or can beelongated to further allow for adjustment of the bevel milling element60. In one embodiment, a plurality of bores are present on millingelement support 42, spaced at predetermined increments to provide formultiple securing locations for bevel milling element 60.

Alternatively and preferably, channel 62 of milling element support 42includes a locking element 68 as shown in FIGS. 3, 4 and 7 which securesbevel milling element 60 to the milling element support 42. Lockingelement 68 is secured to milling element support 42 via one or moresecuring elements 70, thereby fixing the bevel milling element 60 to themilling element support 42 at a desired location in relation theretowith a pressure or compression fit which prevents movement of the bevelmilling element 60. Thus the bevel milling element 60 is secured at alocation in channel 62 between side 63 and locking element 68, withcutting edge 61 facing the bottom end of milling head 30 as shown inFIG. 3.

Bevel milling element 60 or outer diameter milling element 50 can have aneutral, positive or negative rake with a positive rake being preferred.An advantage of the design of milling head 30 is that outer diametermilling element 50 and/or bevel milling element 60 can be replacedeasily once cutting edge 51 and/or 61 becomes worn or the like. Ifdesired, outer diameter milling element 50 and bevel milling element 60have one or more cutting edges which are a chip breaker edge, as knownin the art, that tapers from a thicker portion to a relatively sharppoint to provide a clean finish to the tube end. Bevel milling element60 can have any desired shape so long as the noted beveling function canbe carried out.

As noted, the outer diameter milling element 50 can be positioned at anydesired location along track 54 of milling element support 42. Likewise,bevel milling element 60 can be positioned at generally any desiredlocation along channel 62 of milling element support 42. Thus, the depthand length to which a tube is milled from an end portion thereof can beeasily modified by a user to desired specifications. The distancesbetween bevel milling element 60, cutting edge 61, and outer diametermilling element 50 cutting edges 51, 57 can be adjusted as describedherein to impart a desired finish to a tube end.

The milling heads of the present invention are preferably formedutilizing a CNC machining system. Milling heads 30 are preferably formedfrom a suitable metal such as medium carbon alloy steel, high carbonalloy steel, stainless steel, or similar metals or alloys of metals. Themilling head 30 is preferably formed out of a metal or metal alloysuitable to withstand a heat treating process which generally imparts ahard finish and durability to the milling head. The outer diametermilling element 50 can be formed out of a metal or metal alloy such astool steel or carbide with carbide being preferred, as it provides longblade life and desirable wear characteristics. The bevel millingelements 60 of the present invention can be formed of the same materialsas the outer diameter milling elements but are preferably formed of atool steel.

Methods for utilizing milling head 30 are as follows. After determiningthe dimensions of the tube to be milled, such as inner diameter, outerdiameter, or the like, the milling head 30 outer diameter millingelement(s) 50 and bevel milling element(s) 60 are, individually,adjusted to relation to milling element support 42 and are adapted toimpart a desired finish to the end 12 of a tube 10. Thus, bevel millingelement 60 is adjusted and secured to channel 62 of milling elementsupport 42, or directly to side 63 as described herein. Likewise, outerdiameter milling element 50 is adjusted on guide 52 and secured tomilling element support 42. Milling head 30 is attached through toolmounting portion 32 to a rotary milling tool. Rotary milling toolcontaining milling head 30 is preferably temporarily connected orsecured to the tube to be milled utilizing a collet, or wedge system, orthe like, as known in the art. The milling head 30 is then advancedtowards tube 10, wherein depending on the configuration of the millingelements 50 and 60, contact with the tube is made with at least one ofthe cutting edges thereof. Outer diameter milling element 50 mills apredetermined outer circumference of the tube. Bevel milling element 60contacts the tube end and mills a desired bevel into the tube. Themilling head is further advanced along the tube as the milling operationis performed. Depending on the configuration of the milling elements,any membrane and/or weld overlay present on the surface of the tube isalso removed within the cutting sweep of the milling element cuttingedges 51 and/or 61. After the desired milling operation has beenperformed, the rotary milling tool is disconnected from the tube leavingthe tube having a beveled end and a section where material from theouter diameter of the tube has been removed for a predetermined distanceadjacent the beveled end as illustrated in FIG. 3.

In one embodiment, a gauge 80 is provided as illustrated in FIGS. 8 and9 in order to aid in adjustment of the outer diameter milling element 50present on milling head 30. When two or more outer diameter millingelements 50 are present on the milling head 30, the gauge 80 is utilizedto co-align the multiple elements 50. Gauge 80 includes one or morealignment sections 81, 82 and 83 representing desired incremental stepsthat can be used to set outer diameter milling element 50 on millinghead 30. Each section 81, 82, 83 has at least one surface that islocated a predetermined radial distance from a gauge central axis 85.When gauge 80 is in position in relation to milling head 30 where anouter diameter milling element 50 can be adjusted, gauge central axis 85is aligned or substantially aligned with central axis 31 of milling head30. Each alignment section 81, 82, 83 is preferably located at adifferent radial distance from gauge central axis 85. In one embodiment,adjacent alignment sections have radial differences of about 0.010 inch(0.25 mm), 0.025 inch (0.63 mm) or 0.05 inch (1.27 mm).

Gauge 80 is desirably utilized after milling head 30 has been attachedto a rotary milling tool. Inner surface 84 of gauge 80 is situatedagainst a center shaft of a known diameter of the collet or other wedgesystem utilized. Outer diameter milling element 50 is advanced towardsgauge 80 and a portion thereof is abutted against one of alignmentsections 81, 82 or 83 to provide a desired milling element arrangement.Afterwards, the outer diameter milling element 50 is secured to millinghead 30. This sequence is repeated until all outer diameter millingelements 50 are set in the same position. Afterwards, gauge 80 isremoved and a desired milling operation is carried out.

In accordance with the patent statutes, the best mode and preferredembodiment have been set forth; the scope of the invention is notlimited thereto, but rather by the scope of the attached claims.

1. A milling head for a rotary milling tool, comprising: a body adaptedto be connected to a rotary milling tool; and at least one millingelement support connected to the body, wherein the milling elementsupport is spaced a distance from a central rotational axis of themilling head, wherein a recess extends a distance between the millingelement support and the central rotational axis, wherein the millingelement support includes a channel, and wherein the channel has a backwall that longitudinally extends in relation to the central rotationalaxis of the milling head at an angle of 0° to about 45°; and wherein abevel milling element having a cutting edge adapted to mill a bevel on atube is adjustable in the channel and is secured in the channel via apressure fit.
 2. The milling head according to claim 1, wherein aportion of the bevel milling element contacts the channel back wall. 3.The milling head according to claim 1, wherein the channel includes aside, the back wall, and a locking element, and wherein the bevelmilling element is secured between the channel side and the lockingelement.
 4. The milling head according to claim 3, wherein the lockingelement is secured to the milling element support with a securingelement.
 5. The milling head according to claim 4, wherein the back wallextends longitudinally at an angle from 0° to about 20° with respect tothe central axis.
 6. The milling head according to claim 5, wherein theback wall extends longitudinally at an angle from 0° to about 10° withrespect to the central axis.
 7. The milling head according to claim 5,wherein the bevel milling element cutting edge is fixed at an angle offrom about 20° to about 60° in relation to the central axis.
 8. Themilling head according to claim 7, wherein the bevel milling elementcutting edge is fixed at an angle from about 30° to about 45° inrelation to the central axis.
 9. The milling head according to claim 6,wherein the milling element support further includes a guide, wherein anouter diameter milling element is adjustable in relation to the guideand is secured between the guide and a fixing element, wherein thefixing element is connected to the milling element support by a securingelement, and wherein the outer diameter milling element has a cuttingedge adapted to remove material from the outer diameter of the tube. 10.The milling head according to claim 9, wherein the guide includes atrack that extends longitudinally at an angle measured perpendicular tothe central rotational axis of the milling head of from 0° to about 45°.11. The milling head according to claim 10, wherein a portion of theouter diameter milling element contacts the track and is movable alongthe track before being secured to the milling head and, wherein onecutting edge of the outer diameter milling element has a longitudinalaxis that is fixed at an angle with respect to the central axis of themilling head of 0° to about 30°.
 12. A method for milling a tube,comprising the steps of: providing a tube having an end portion;providing a rotary tool having a milling head comprising a body adaptedto be connected to a rotary milling tool, wherein the body has anannular recess and one or more milling element supports connected to thebody, wherein at least one milling element support includes a channel,wherein a bevel milling element having a cutting edge is adjustable inthe channel, wherein the bevel milling element is connected via apressure fit in the channel between a side of the milling elementsupport and a locking element, wherein at least one milling elementsupport includes a guide, wherein an outer diameter milling elementhaving a cutting edge is adjustable in relation to the guide, whereinthe outer diameter milling element is connected to the guide via apressure fit between a back of the milling element support and a fixingelement, wherein the bevel milling element has an annular cutting sweepthat is at least concentric with an inner end of a cutting sweep of theouter diameter milling element and radially inward a distance from theouter diameter milling element cutting sweep; adjusting at least one ofthe outer diameter milling elements or bevel milling elements inrelation to the milling head body and securing the at least one elementto the milling head; and milling the end portion of the tube by removingmaterial from an outer diameter of the tube and placing a bevel on theend of the tube.
 13. The method for milling a tube according to claim12, including the step of removing from about 1% to about 50% of anannular thickness of the tube with the milling head.
 14. The method formilling a tube according to claim 12, including the step of utilizing agauge to set at least one of the milling head milling elements.